7,991 research outputs found

    Dissipation of Quantum Turbulence in the Zero Temperature Limit

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    Turbulence, produced by an impulsive spin-down from angular velocity Omega to rest of a cube-shaped container, is investigated in superfluid 4He at temperatures 0.08 K - 1.6 K. The density of quantized vortex lines L is measured by scattering negative ions. Homogeneous turbulence develops after time t of approximately 20 \Omega and decays as L proportional to t^(-3/2). The corresponding energy flux epsilon = nu' (kappa L)^2, which is proportional to t^(-3), is characteristic of quasi-classical turbulence at high Re with a saturated energy-containing length. The effective kinematic viscosity in the T=0 limit is nu' = 0.003 kappa, where kappa=10^(-3) cm^2 / s is the circulation quantum.Comment: 4 pages, 5 figures. Updated following referees comment

    Phase Diagram of Multilayer Magnetic Structures

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    Multilayer "ferromagnet-layered antiferromagnet" (Fe/Cr) structures frustrated due to the roughness of layer interfaces are studied by numerical modeling methods. The "thickness-roughness" phase diagrams for the case of thin ferromagnetic film on the surface of bulk antiferromagnet and for two ferromagnetic layers separated by an antiferromagnetic interlayer are obtained and the order parameter distributions for all phases are found. The phase transitions nature in such systems is considered. The range of applicability for the "magnetic proximity model" proposed by Slonczewski is evaluated.Comment: 8 pages, 8 figure

    Resonantly suppressed transmission and anomalously enhanced light absorption in ultrathin metal films

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    We study light diffraction in the periodically modulated ultrathin metal films both analytically and numerically. Without modulation these films are almost transparent. The periodicity results in the anomalous effects, such as suppression of the transmittance accompanied by a strong enhancement of the absorptivity and specular reflectivity, due to excitation of the surface plasmon polaritons. These phenomena are opposite to the widely known enhanced transparency of periodically modulated optically thick metal films. Our theoretical analysis can be a starting point for the experimental investigation of these intriguing phenomena.Comment: 4 pages, 5 figure

    Making the Best of Polymers with Sulfurā€“Nitrogen Bonds: From Sources to Innovative Materials

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    Polymers with sulfurā€“nitrogen bonds have been underestimated for a long time, although the intrinsic characteristics of these polymers offer a myriad of superior properties (e.g., degradation, flame retardancy, filmā€forming ability, good solubility in polar solvents, and high refractivity with small chromatic dispersions, among other things) compared to their carbon analogues. The remarkable characteristics of these polymers result from the unique chemical properties of the sulfurā€“nitrogen bond (e.g., its polar character and the multiple valence states of sulfur), and thus open excellent perspectives for the development of innovative (bio)materials. Accordingly, this review describes the most common chemical approaches toward the efficient synthesis of these ubiquitous polymers possessing diverse sulfurā€“nitrogen bonds, and furthermore highlights their applications in multiple fields, ranging from biomedicine to energy storage, with the aim of providing an informative perspective on challenges facing the synthesis of sulfurā€“nitrogen polymers with desirable properties

    Influence of antidysbiotic drugs on the liver of rats with experimental non-alcoholic steatohepatitis

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    High-fat diets combined with the introduction of lincomycin causes the development of steatohepatitis. Introduction antidysbiotic drugs (pro- and prebiotics) has a therapeutic effect
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